Recently discovered carbon nanotube has a great possibility of application in a variety of fields including energy industry, environmental and electronic materials, owing to its excellent mechanical strength, thermal conductivity, electrical conductivity and chemical stability. In 1991, Dr. Lijima of NEC, Japan, studied carbon mass formed on negative electrode by arc-discharge under TEM, during which he fount out a long thin rod shaped carbon nanotube and later on he published a paper on this in Nature, which was the first report of carbon nanotube. Carbon nanotube is that graphite side is rolled with nano-size diameter and according to the angle and structure of this rolled graphite side, it shows the characteristics of metal or semiconductor. Carbon nanotube is expected not only as a novel medical material owing to its affinity to biotissues but also as an applicable material for ultrafine link, ultrafine pipe, ultrafine liquid injection device, and gas sensor. Studies on the application of carbon nanotube as electron emission source and field emission display (FED) are most actively undergoing. Besides, studies on the application of carbon nanotube as a raw material for fuel cell and secondary cell, expected as alternative energy source, and as a bulk material requiring light weight but high strength are also actively undergoing.
Carbon nanotube-metal composite is a novel material which is applicable as a material in the field of electronic industry, precisely as an electrode material for field emission display, fuel cell and solar cell, for hydrogen storage device of fuel cell, for electromagnetic interference shielding device and as a raw material for electronic ink.
This composite is also expected to be a new enhanced material having light weight but high strength so that it is applicable to high strength lightweight tool steels and automobile parts, and as a material for defense industry.
Carbon nanotube-metal composite is a novel material prepared by inducing functional group in carbon nanotube and by reacting the induced functional group with a metal (Co, Cu, Ni, etc). Owing to the metal component included therein, the composite demonstrates excellent properties favoring various application, for example the productions of field emission display, hydrogen storage device assembly, electrode, super capacitor, electromagnetic interference shielding device, and high strength light weight applied product. If a metal particle to be bound is in nano-size, the metal properties are changed. The most peculiar change in physical properties of metal is decrease of melting point. And the melting point is further lowered as the size of nano-metal particle becomes smaller. Accordingly, the carbon nanotube composite has different properties from the conventional materials, providing diverse applicability as a novel material:
According to the request of a novel material, a carbon nanotube-metal composite is developed by physical mixing and sintering carbon nanotube with a metal (P. J. F. Harris, International Materials Reviews, Vol 49, p31-43, 2004).
However, in this composite, metal is not bound to carbon nanotube and dispersed irregularly with forming lumps, making this composite less favorable as a novel material. Recently there has been another attempt to prepare a composite by binding metal chemically to carbon nanotube. But, in this method, the metal covers the whole carbon nanotube, so that characteristics of carbon nanotube are buried.
In the meantime, Korean Patent No. 616071 and No. 778094 describe a method for reducing a metal precursor by using a reducing agent in carbon nanotube dispersing solvent. However, the above patents also have a problem that reduction by the added reducing agent does not occur regularly in the reaction solution, so that the produced carbon nanotube-metal composite has poor dispersibility and irregularity in metal particle size.